This invention relates to image formation using a photographic silver halide light-sensitive material. More particularly, it relates to a method for forming an image in a plate making photographic silver halide light-sensitive material whereby a superhigh contrast image suitable for printing process photography can be consistently produced.
The photographic plate making procedure requires an image forming system capable of providing superhigh contrast photographic characteristics to achieve satisfactory reproduction of a continuous tone image by a halftone dot image or reproduction of a line image.
In the prior art, a special developer solution called a lith developer is used for this purpose.
The lith developer contains hydroquinone as a sole developing agent. In order that the infectious development of hydroquinone is not disturbed, a sulfite salt is used as a preservative in the form of an adduct with formaldehyde so as to minimize the concentration of free sulfite ions. Thus the lith developer has the serious drawback that it is quite liable to aerial oxidation and cannot be shelf stored over 3 days.
One known method for obtaining superhigh contrast photographic characteristics using a stable developer is by using hydrazine derivatives as described in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,221,857, 4,243,739, etc. This method can provide photographic characteristics with superhigh contrast and high sensitivity and allows a high concentration of a sulfite salt to be added to the developer so that the stability of the developer against air oxidation is outstandingly improved over the lith developer.
The hydrazine derivatives exert their effect of rendering the contrast super high and increasing sensitivity only when the developer is in a high pH range. However, such a high pH level undesirably leads to a reduced effective life of the developer.
For the high pH developers, a phosphate salt is well known as a buffer and widely used because of low cost.
On the other hand, a fixer solution containing a water-soluble aluminum salt as a hardener is used in order to mitigate the load of drying treated photosensitive materials in processing with an automatic developing machine or processor, particularly often used in rapid processing. Although the phosphate salt has a high buffering ability at a high pH range as mentioned above, a hardening fixer solution cannot be used in combination with it. When a phosphate is used in combination with a fixer containing an aluminum salt as a hardener, there is formed a precipitate of aluminum phosphate to leave white deposits on the associated roller, which are transferred to the treated photosensitive material. Although a variety of buffering agents have been tested for high pH developers, no inexpensive substitute for phosphate salts has been discovered. Thus, the high pH developer is used at the sacrifice of ease of drying in processing with an autoprocessor.
As the above problem indicates, the use of a high pH developer has several troubles due to the maintenance of pH at such a high level. If there is available a developer which has an extended effective life in addition to high performance and high stability and which can be used at a sufficient pH range to dispense with a phosphate salt, such a contrast enhancing developer would be very useful.
U.S. Pat. No. 4,269,929 discloses a method of supplying a contrast promoting amount of an amine during development of the photographic silver halide material containing hydrazine derivatives. However, the amines are undesirable because they often produce an unpleasant odor. The amines can reduce the pH of the developer only to a small extent.
There is a need for developing a method capable of establishing a high pH level during development without sacrificing the shelf storage and stability of a developer.
Japanese Patent Application Kokai No. 56-89736 discloses a method in which a silver halide photosensitive material having a hydrazine compound and a dihydroxybenzene developing agent incorporated therein is treated with an alkaline activator.
However, a highly alkaline activator treating solution having a pH of at least 11.5, particularly 12 to 14 is required in order to obtain a sufficiently high contrast image. The alkaline activator treating solution having such a high pH value tends to reduce its pH by absorbing carbon dioxide in air during storage or treatment. High pH solutions are dangerous to human bodies and the environment.